Wireless backhaul networks are deployed to carry the traffic between a wireless access network and the core network. For example, a wireless backhaul network may comprise a plurality of hubs, each connected to the wired core network via Ethernet. Each hub serves multiple Remote Backhaul Modules (RBMs), in a Point-to-Multipoint (PtMP) or Point-to-Point (PtP) configuration, using a wireless channel. Each RBM is deployed close to an access network base station, such as a small cell base station, and connected to the base station via a cable. The hubs are deployed at the locations where wired high capacity access to the core network is available, e.g. at a fiber point-of-presence.
In a wireless backhaul network, the term cluster refers to a number of RBMs and their respective serving hub. Performance of an RBM such as throughput is contingent upon its received Carrier-to-Interference-plus-Noise Ratio (CINR) and the amount of bandwidth allocated to this RBM given a selected carrier. The received signal strength of an RBM is determined by the transmit power of its serving hub and the pathloss between the serving hub and the RBM. The received interference-plus-noise level of an RBM is determined by the transmit powers of all the interfering hubs and the pathlosses between interfering hubs and the RBM. An RBM is affected by an interfering hub when a desired signal and an interfering signal are transmitted over the same carrier frequency.
Such a network typically operates in an interference rich environment. Interference may arise from co-channel or intra-link interference between radio links within the backhaul network. Additionally, there will be co-channel interference from other networks, i.e. inter-network interference.
In orthogonal frequency division multiple access (OFDMA) wireless networks, the frequency resources are divided into subcarriers or tones. In frequency reuse of 1 multi-sector deployment, network performance such as throughput, fairness and coverage in an interference-limited radio environment may be mitigated by techniques such as disclosed in the current Applicant's above-referenced related patents and patent applications.
Various different frame structures and/or signalling methods are known for operation of wireless networks using Point-to-Point (PtP) transmission and Point-to-Multipoint (PtMP) transmission. For application to fixed wireless backhaul networks, classic PtMP frame structures, as used conventionally for access networks using WiFi, LTE or WiMAx standards, have issues with overhead, latency and scalability. Thus, there is a need for novel frame structures and signalling methods to facilitate Point-to-Multipoint (PtMP) transmission in wireless backhaul networks.
An object of the present invention is to provide an improved or alternative method and system for signalling to enable Point-to-Multipoint (PtMP) transmission in a wireless backhaul network, and particularly for wireless backhaul networks comprising fixed or stationary nodes with directional antennas, including small cell Non-Line-Of-Sight (NLOS) backhaul networks.